Could Small Changes in Land Use Cause Large Shifts in Vehicle Ownership?

Land-use patterns are complex. Diverse forces such as culture, economics, psychology, history, policy, and other factors act in parallel upon the same parcels of land, producing diverse land types that are not easy to describe. However, breaking out land-use into three simple types according to Census geographical classifications—cities, suburbs, and rural—reveals that household vehicle ownership increases substantially from cities to suburbs to rural areas.

The data in the above chart gives rise to the following question: Which key variables are associated with such wide shifts in vehicle ownership per land-use? Research shows that the following geographic and economic variables are closely correlated with vehicle ownership differences by land-use type:

Population Density (population per square mile)

Housing Density (occupied housing units per square mile)

Household Income (annual median)

Population density, housing density, and median household income help to translate “soft” intangibles of urban design into a “hard” impact on numerical indicators. Because people make decisions at the margin, how large do changes in these variables need to be in order for large changes in vehicle ownership levels to occur? Given that the Census Bureau predicts an increase in population of roughly 100 million people between 2015 and 2060, it is important to have a cohesive framework to evaluate how changes in land development may impact vehicle ownership levels over time.

This article will present statistical correlations between population density, housing density, household income, and vehicle ownership per land-use, followed by an assessment of impact on vehicle ownership decisions.

Density: Inverse correspondence with vehicle ownership

Density takes on two standard measurable forms—population and housing. Each statistic shows an inverse correspondence with vehicle ownership. For population density, the more people that live in a given area, the less vehicle ownership is in that area; for housing density, the more occupied housing units that are in a given area, the less vehicle ownership there is. This negative correlation is most likely because less land per person (i.e. higher population density) and less distance between households (i.e. higher housing density) imply shorter travel distances and less need for personal vehicles in order to carry out daily tasks. The most recent density data comes from the 2010 decennial census and can be seen in the following charts:

Household income: Direct correspondence with vehicle ownership

Household income shows a direct correspondence with vehicle ownership. That is, suburban and rural areas both have higher median incomes and higher vehicle ownership rates, on average, than cities, matching the higher rates of vehicle ownership in suburbs and rural areas.

Suburban and rural areas both have higher median incomes and higher vehicle ownership rates, on average, than cities, matching the higher rates of vehicle ownership in suburbs and rural areas.

As households become wealthier, they can afford to live in the more spread-out suburban areas, and thus they can afford to purchase vehicles to account for the longer distances and lower densities. In rural areas, incomes are higher than cities, though not by as great a difference as in suburbs. Even so, higher rural household incomes coincide with far lower density to incentivize a very high level of household vehicle ownership.

Can Vehicle Ownership Levels Change? Analysis “at the margin”

The correlations between the three variables above (population density, housing density, household income) and vehicle ownership, according to land-use type, can be sharpened further by breaking out vehicle ownership levels more specifically in each land-use type. Economics teaches that decisions happen at the margin. Initial costs are fixed but marginal costs are variable. People weigh the last additional benefits and costs more closely. The following graph strongly suggests an analysis “at the margin”:

Because this chart provides highly specific visibility of the proportions of vehicles per household, it becomes possible to concretely imagine what a marginal reduction in vehicle ownership might look like, according to each specific land-use type. For instance:

City: Can more than 15 percent of city households be persuaded to go without a vehicle?

Suburbs: Do 24 percent of suburban households really need three or more vehicles?

Rural: Do 11 percent of rural households really need to have four or more vehicles?

To put these questions in further perspective, it is worth noting how much of the U.S. population lives within each land-use type:

Looking at the population numbers reveals the extent to which marginal changes in household vehicle ownership could affect national patterns. What if small changes in population density, housing density, or household income lead to a decision to drop the last marginal vehicle? How many people would this affect, and in which locations?

Suburbs and cities together comprise metropolitan areas, including over 85 percent of U.S. population in 2016. As metropolitan areas are the locale where most future U.S. population growth will likely take place, the dance between low-density suburban and high-density urban settlement becomes an important juncture that can possibly stimulate marginal changes in vehicle ownership. If future population growth occurs in suburbs of lower-density and higher income, then vehicle ownership will likely remain higher, whereas if future population growth gathers in higher density, lower income cities, vehicle ownership will likely be lower. There is the additional question of whether, within suburbs themselves, long-running trends towards “urbanization of the suburbs” can provoke changes toward higher density, lower-income suburbs. Such a trend may result in lower vehicle ownership in future decades in America’s metropolitan areas.

Comparing cities with rural areas, on the other hand, reveals a starker contrast. In rural areas, trends are likely to remain constant, because the immense distances and very low densities necessitate higher numbers of vehicles. In stark contrast to rural areas, cities constitute the place where people are the most likely to give up their vehicles, due to higher densities leading to availability of other options such as public transit, walking, biking, or ride-sharing.

Conclusion: Variables to track

The future of U.S. land-use patterns could have a significant impact upon vehicle ownership. Translating complex configurations of land-use into concrete variables trackable by policymakers could prove very useful in monitoring the development of the situation. Can incremental adjustments in population density, housing density, or household income cause millions of households to give up their last marginal vehicle? What is the impact of whether these changes in density or income occur in a city, suburb, or rural area? These variables will be key factors in assessing vehicle ownership trends and the future of transportation.

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The Fuse is an energy news and analysis site supported by Securing America’s Future Energy. The views expressed here are those of individual contributors and do not necessarily represent the views of the organization.

Issues in Focus

Safety Standards for Crude-By-Rail Shipments

A series of accidents in North America in recent years have raised concerns regarding rail shipments of crude oil. Fatal accidents in Lynchburg, Virginia, Lac-Megantic, Quebec, Fayette County, West Virginia, and (most recently) Culbertson, Montana have prompted public outcry and regulatory scrutiny.

2014 saw an all-time record of 144 oil train incidents in the U.S.—up from just one in 2009—causing a total of more than $7 million in damage.

The spate of crude-by-rail accidents has emerged from the confluence of three factors. First is the massive increase in oil movements by rail, which has increased more than three-fold since 2010. Second is the inadequate safety features of DOT-111 cars, particularly those constructed prior to 2011, which account for roughly 70 percent of tank cars on U.S. railroads. Third is the high volatility of oil produced from the Bakken and other shale formations, which makes this crude more prone towards combustion.

Of these three, rail car safety standards is the factor over which regulators can exert the most control. After months of regulatory review, on May 1, 2015, the White House and the Department of Transportation unveiled the new safety standards. The announcement also coincided with new tank car standards in Canada—a critical move, since many crude by rail shipments cross the U.S.-Canadian border. In the words DOT, the new rule:

Since the rule was announced, Republicans in Congress sought to roll back the provision calling for an advanced breaking system, following concerns from the rail industry that such an upgrade would be unnecessary and could cost billions of dollars. The advanced braking systems are required to be in place by 2021.

Democrats in Congress have argued that the new rules are insufficient to mitigate the danger. Senator Maria Cantwell (D-WA) and Senator Tammy Baldwin (D-WI) both issued statements arguing that the rules were insufficient and the timelines for safety improvements were too long.

The current industry standard car, the CPC-1232, came into usage in October 2011. These cars have half inch thick shells (marginally thicker than the DOT-111 7/16 inch shells) and advanced valves that are more resilient in the event of an accident. However, these newer cars were involved in the derailments and explosions in Virginia and West Virginia within the past year, raising questions about the validity of replacing only the DOT-111s manufactured before 2011.

Before the rule was finalized, early reports indicated that the rule submitted to the White House by the Department of Transportation has proposed a two-stage phase-out of the current fleet of railcars, focusing first on the pre-2011 cars, then the current standard CPC-1232 cars. In the final rule, DOT mandated a more aggressive timeline for retrofitting the CPC-1232 cars, imposing a deadline of April 1, 2020 for non-jacketed cars.

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DataSpotlight

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This view is misguided. While some forecasts project that the United States could become a self-sufficient oil producer within the next decade, this remains a distant prospect. According to the April 2015 Short Term Energy Outlook, total U.S. crude oil production averaged an estimated 9.3 million barrels per day in March, while total oil demand in the country is over 19 million barrels per day.

This graphic helps illustrate the regional variations in crude oil supply and demand. North America, Europe, and Asia all run significant production deficits, with the Middle East, Africa, Latin America, and Former Soviet Union are global engines of crude oil supply.